{"id":28615,"date":"2025-05-20T09:56:50","date_gmt":"2025-05-20T08:56:50","guid":{"rendered":"https:\/\/www.ch.ic.ac.uk\/rzepa\/blog\/?p=28615"},"modified":"2025-05-20T09:56:50","modified_gmt":"2025-05-20T08:56:50","slug":"5-imino-5%ce%bb4-heptathiepane-3-oxide-more-exuberent-anomeric-effects","status":"publish","type":"post","link":"https:\/\/www.rzepa.net\/blog\/?p=28615","title":{"rendered":"5-Imino-5\u03bb4<\/sup>-heptathiepane 3-oxide. More exuberent anomeric effects."},"content":{"rendered":"
\n

The two previous \u00a0posts[1]<\/a><\/span>,[2]<\/a><\/span> on the topic of anomeric effects in 7-membered sulfur rings illustrated how orbital interactions between the lone pairs in the molecules and S-S bonds produced widely varying S-S bond lengths in the molecules, some are shorter than normal (which is ~2.05\u00c5 for e.g.<\/em> the S8<\/sub> ring) by ~ 0.1\u00c5 and some are longer by ~0.24\u00c5. Here we extend this to the unknown molecule shown below.<\/p>\n

\"\"<\/a><\/p>\n

The usual \u00a0MN15L\/Def2-TZVPP calculation[3]<\/a><\/span> gives the calculated geometry shown below. In parentheses are the calculated S-S vibrational wavenumbers (some are marked with ~ since these modes are contaminated by mixing with other parts of the molecules).<\/p>\n

\"\"<\/p>\n

The interaction energies between the donor and acceptor, E(2), are shown below. Numbers 5-8 are the same as was identified for the parent molecule S7<\/sub>, but the energies have increased substantially (previously 12.3\/10.1 kcal\/mol). The Wiberg bond index for the strongest bond (S2-S3) is 1.276 and the weakest (S1-S2) is 0.610, quite some variation! Given that the known S7<\/sub>O was already very unstable[4]<\/a><\/span>, it seems unlikely that the probably even more unstable S7<\/sub>ONH could ever be isolated, but there is a challenge!<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
#<\/th>\nAcceptor S-S bond<\/th>\nDonor Lp<\/th>\nNBO E(2) Energy<\/th>\n<\/tr>\n
1<\/td>\nS4-S5<\/td>\nO8<\/td>\n31.9<\/td>\n<\/tr>\n
2<\/td>\nS1-S2<\/td>\nN9<\/td>\n29.6<\/td>\n<\/tr>\n
3<\/td>\nS1-S6<\/td>\nN9<\/td>\n27.0<\/td>\n<\/tr>\n
4<\/td>\nS5-S6<\/td>\nO8<\/td>\n20.4<\/td>\n<\/tr>\n
5<\/td>\nS4-S5<\/td>\nS7<\/td>\n16.8<\/td>\n<\/tr>\n
6<\/td>\nS1-S2<\/td>\nS3<\/td>\n16.4<\/td>\n<\/tr>\n
7<\/td>\nS3-S7<\/td>\nS2<\/td>\n15.4<\/td>\n<\/tr>\n
8<\/td>\nS3-S7<\/td>\nS4<\/td>\n15.2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

There are numerous compounds with six, seven and eight membered sulfur rings, and it would always be worth keeping an eye out for unusually short or long S-S bonds in them, since they may well be more manifestations of these sulfur anomeric effects.<\/p>\n

References<\/h2>\n
  1. H. Rzepa, \"Cycloheptasulfur sulfoxide, S<sub>7<\/sub>O \u2013 Anomeric effects galore!\", 2025. https:\/\/doi.org\/10.59350\/rzepa.28515<\/a>\n\n<\/li>\n
  2. H. Rzepa, \"Cyclo-Heptasulfur, S<sub>7<\/sub> \u2013 a classic anomeric effect discovered during a pub lunch!\", 2025. https:\/\/doi.org\/10.59350\/rzepa.28407<\/a>\n\n<\/li>\n
  3. H. Rzepa, \"S7O2 NBO7 Cs symmetry\", 2025. https:\/\/doi.org\/10.14469\/hpc\/15235<\/a>\n\n<\/li>\n
  4. R. Steudel, R. Reinhardt, and T. Sandow, \"Bond Interaction in Sulfur Rings: Crystal and Molecular Structure of <i>cyclo<\/i>\u2010Heptasulfur Oxide, S<sub>7<\/sub>O\", Angewandte Chemie International Edition in English<\/i>, vol. 16, pp. 716-716, 1977. https:\/\/doi.org\/10.1002\/anie.197707161<\/a>\n\n<\/li>\n<\/ol>\n\n<\/div> ","protected":false},"excerpt":{"rendered":"

    The two previous \u00a0posts, on the topic of anomeric effects in 7-membered sulfur rings illustrated how orbital interactions between the lone pairs in the molecules and S-S bonds produced widely varying S-S bond lengths in the molecules, some are shorter than normal (which is ~2.05\u00c5 for e.g. the S8 ring) by ~ 0.1\u00c5 and some […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[6],"tags":[],"class_list":["post-28615","post","type-post","status-publish","format-standard","hentry","category-interesting-chemistry"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1gPyz-7rx","jetpack_likes_enabled":true,"_links":{"self":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/28615","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=28615"}],"version-history":[{"count":0,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=\/wp\/v2\/posts\/28615\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=28615"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=28615"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rzepa.net\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=28615"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}